In processes for coating a strip with liquid coating material, a gas barrier assembly is often used to wipe off the excess coating and thereby control the thickness of coating remaining on the strip. The assembly includes a header with a gas barrier orifice; a frame structure for supporting the header in position adjacent to the strip, and a gas supply connected to the header. Recently, the orifice of the header has been designed with a curved lip configuration so that more uniform coating thickness is obtained across the strip width. U.S. Pat. No. 3,670,695 may be referred to for a showing of such a header. A particular curved lip configuration provides a optimum results however, for only a limited range of strip widths. Therefore, it is desirable to change to a header having a different lip configuration when strip outside a certain width range is to be coated.
Changing headers in present gas barrier assemblies is time consuming and causes substantial loss of production on the coating line because the change requires removing the entire frame containing the headers from the coating line, and moving it to a maintenance area. All electrical and piping connections must of course be disconnected before the frame can be moved. At the maintenance area the header is removed from the frame and a replacement installed. The frame is then transported back to the line, and the various electrical and piping connections made. This whole operation usually requires 2 to 3 hours or more overall.
Of course at times it is necessary to change headers, for maintenance purposes, such as when dirt gets into the system and clogs the orifice or when other problems occur. Header changes in these situations also require the same time consuming steps on present equipment and therefore also cause substantial loss of production.